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[Martin (Admin)]

Hi All,

We've just spent a week scrapping about 50 laptops, can the good batteries be used as the main battery for model boats?
What are Li-on batteries (Lithium-ion) characteristics?

[nick_75au]

Hi Martin,
Good batteries, much more robust than the Li poly style but they dont have high C ratings maybe 2 -4 C depending on type, the blue Sony Enertec H2 18650 are about 1300 mA and are fairly poor in comparison to the green panasonic ones which from memory are 2200 mA or so.Both these type are the ones that I have.
Otherwise similar discharge and charge characteristics as Lipo. Voltage is maximum 4.1 on charge as opposed to 4.2 and nominal voltage at 3.6 rather than 3.7
Ive obtained several that show 0 volts. I remove all the protection circuitry then zap them quickly with a 12 volt battery until they read a voltage then charge them at 1 C on my Swallow charger on the Li-ion stting, they have all come to life again. I cant say wether they have full capacity but they all hold voltage and supply good current even after not touching them for a couple of months.
Conclusion, good battery's for low demand scale boats where weight is important, not good for fast electric. easy to get high voltage configurations due to the 3.6 nominal voltage in a small package. would make excellent TX packs as a 3 cell

caveat lector,(let the reader beware) I've never had a problem zapping the batteries but it isn't something I would recommend to the inexperienced, no doubt someone will have a story about this being unsafe.

Regards Nick

[nick_75au]

By the way they are also don't need to be balanced charged like lipos every time, it pays to check them occasionally however, charging 1 cell at a time/balancing if there are voltage differences.
Hope this is useful
Regards
Nick

[andrewh]

Martin,

Basically that's a YES.  Nick has summarised neatly - they are generally comnnected as 2 parallel paths in Laptop batteries, and seen to be Li-ion cells around 1500mah (per cell) with, as nick says quite a low current capability.

I have never found a suspect cell in all the laptop batteries I have eviscerated, but if I did I would either follow nick's advice or dispose of it (carefully and responsibly). 
I have, however made several boat packs of two cells in series (2s;1P) so that I had 7V nominal and about 1500 mah capacity and I use these for S400 motors presumably taking a bit less than 10Amps. 
This is TOO MUCH to take out of the cells - the voltage sags something terrible so I am abusing them splendidly.  This very much confirms the  current rating as 2 to 4C maximum
I should have soldered two sets in parallel to get 2S;2P setup (7V, 3000mah)

They would be absolutely ideal for boats where weight and bulk are a problem (grey funnel line, plastic magic, narrow hulls etc) and the current required is not too high, or alternatively where you want a lot of volts or capacity in a hull by making a stack them in series (6S is close to 24 Volts)  THINKS - 3 would drive a smoke generator well without needing the weight of a Lead-acid battery

andrew

[nick_75au]

Green Panasonic ones doing something useful(for the wife)
She brought one of those Roomba robotic vacuum cleaners "refurbished" well the battery pack lasted about a month before loosing capacity It was getting about 45 minutes before it stopped down to 5 minutes after the month.

I opened up the plastic casing and low and behold there are 12 2500ma AA batteries soldered together in the worst way and newspaper stuffed inside. It turns out that the battery normally has a 12 cell sub C  pack. I got the 8 green cells and it turns out they neatly fit in the same space. Made up the pack and let her rip. 2.5 hours later the Roomba said "Ive had enough". Measured the pack voltage and its still 13.5 volts. Not bad from a dead laptop pack.

The wife is very very happy 

Nick

PS Martin I think this topic should be in the batteries forum